Tornado in Oklahama Essay Example for Free

Tornado in Oklahama Essay Tornadoes are violent rotating column of air extending from a thunderstorm to the ground. Tornadoes are known to cause a lot of destruction depending on how violent it occurs. Tornadoes are more common in the United States than any other country. United States receives more than one thousand two hundred tornadoes annually. Most tornadoes in the United States occur in Tornado Alley; an area including states of Oklahama, Texas, Missouri and Kansas. This piece of work will mainly dwell on comparison of data of tornadoes occurring in states of Oklahama, Arkansas, Kansas and Missouri. METHODS Quantitative Data Analysis This is the method used to correct this piece of work where the various portions of the data where collected from records Time series: the information used to conduct this study was done over a period of time where tornadoes frequency, fatality, injuries and number of deaths are indicated. RESULTS Compared with other states, Oklahama ranks number 2 for frequency to tornadoes, 7 for number of death,9 for injuries and 5 for cost of damages. If we compare this statistics to other states by frequency per square mile, Oklahama ranks number 2 for frequency of tornadoes, number 10 for fatalities, number 15 for injuries per square and number 4 for cost per area. The state of Missouri ranks number 8 for frequency, 12 for number of deaths, 15 for injuries and 9 for cost of damage. Comparing with statistics of other states by frequency per square mile, Missouri ranks number 13 for frequency of tornadoes, 14 for fatalities, 19 for injuries per square and 15 for cost per area. In Kansas we have it ranked 3 for frequency of tornadoes, 8 for number of deaths, 14 for injuries and 3 for cost of damage. In comparison with statistics of other states it ranks number 4 for frequency of tornadoes, 13 for fatalities, 22 for injuries per area and 8 for cost per area. Arkansas is ranked number 16 for frequency of tornadoes, 8 for number of deaths, and 14 for injuries 3 for cost of damage. When compared with statistics of other states by frequency per square mile, Arkansas ranks number 16 for frequency of tornadoes, 5 for fatalities, 7 for injuries per square and 16 per cost per area.

Path Planning Strategy For Line Follower Computer Science Essay

Path Planning Strategy For Line Follower Computer Science Essay This paper presents the development of a line follower wheeled mobile robot. In this project, ARM cortex-3 based microcontroller is chosen as the main controller to react towards the data received from infrared line sensors to give fast, smooth, accurate and safe movement in partially structured environment. A dynamic PID control algorithm has been proposed to improve the navigation reliability of the wheeled mobile robot which uses differential drive locomotion system. The experimental results show that the dynamic PID algorithm can be performed under the system real-time requirements. Keywords embedded system, wheeled mobile robot, PID control algorithm. Introduction Embedded system includes many areas of knowledge, microcontroller hardware and software, interfacing technologies, automatic control theory, and sensor technologies etc. To speed up the learning process and motivate students to learn actively, the project-based learning approach may be applied in the embedded system design laboratory [1-4]. The low-cost wheeled mobile robot building, which is proposed in this paper, serves as a good example on which students can learn embedded system design skills. It covers not only common embedded system peripherals, but also energy control and real-time control firmware implementation. The process of the construction of wheeled mobile robot can give students the idea that hardware circuits and software algorithms are both mandatory for a successful embedded system design. The competition between student groups in the racing contest can also encourage them to explore in depth the skills acquired in this laboratory as well as give them lots of fun [ 5-7]. The remainder of this paper is organized as follows: The line follower robot structure and architecture issues and challenges along with their technical issues and problems are discussed in section 2. Programming details will be explained in section 3. Section 4 describes the integration of the complete system. LÄ ±ne follower wheeled MobÄ ±le Robot structure Generally, the line follower robot is one of the self-acting wheeled mobile mechanisms that follow a line drawn on the floor. The route can be a visible black line on a white surface or vice versa. The simple operations of the wheeled mobile line follower robot are shown below. Taking the line position data with optical sensors attached at the front end of the mobile robot. Most are using more than a few numbers of IR photo-reflectors. Therefore, the line sensing procedure needs high resolution and high robustness. Steering the wheeled mobile robot to track the line with any direction-finding mechanism. This is just a servo maneuver; actually, any phase recompense will be required to become stable following motion by applying digital PID filter or any similar servo algorithm. Monitoring the speed according to the path complaint. The speed is restricted during passing a turn due to the friction of the tire with the floor. From actually building the robot platform, to setting up, programming, and hardware or software fine tuning, everything needs to be taken into account when building a differential wheeled mobile robot. A mobile robot can be considered fundamentally as a combination of five main portions and subsystems. Chassis and body. Sensors and signal processing circuits. Microcontroller and interface circuits. Motor drivers Actuators (Motors and wheels) The Chassis and Body The Chassis would be the first part of a robots body. It is designed to handle all of the other components, transmission mechanisms, electronics and battery. It needs to be sufficiently large and provide adequate fixtures to furnish all necessary parts, as well as sturdy enough to cope with the weight of the parts along with additional loads which can appear in dynamic conditions such as vibrations, shocks or chassis torsion and actuators torque. There are some good materials for designing robots such as plastic, aluminum and carbon-composites. We must pay attention to the resistance, weight and mechanical ability for choosing one of them. In the designed robot, printed circuit board (PCB) has been used for chassis because of its lightweight and being strong enough for robot project. All components can be installed on the PCB to minimize the weight. It is noted that the performance is much more valuable than other issues. Sensors and Signal Processing Circuit Line follower robot uses Infrared Ray (IR) sensors to find the path and direction. IR sensors include an infrared transmitter and infrared receiver pair. IR sensors are often used to identify white and black surfaces. White surfaces effectively reflect well, but black surfaces reflect poorly. Hence, the distance between sensors and ground surface is important, and it is more valuable that how we put sensors near to each other. The distance between sensors and ground surface must be 2 to 10 mm, and the distance between each sensor is dependent on the line width. In the designed robot, we have used eight sensors, and they have a suitable distance between each other. If the line width is narrow, the distance between sensors must be reduced; otherwise, while curving the line, the robot will not be turned on time. Generally, the received signals from the sensors are analog and must be converted to the digital form. Therefore, the designed signal processing circuit can send the sensors signals to the microcontroller directly. Microcontroller We have used the TI Stellaris microcontroller LM3S811 in robot project. The LM3S811 microcontroller has a Reduced Instruction Set Coding (RISC) core. Internal oscillators, timers, UART, USB, SPI, pull-up resistors, pulse width modulation, ADC, analog comparator and watch-dog timers are some of the features [8]. With on-chip in-system programmable Flash and SRAM, the LM3S811 is a perfect choice in order to optimize cost. Motor Drivers A well-known and suitable motor driver is IC L298 which can be used to control two motors. It is a high voltage, high-current dual full-bridge driver designed to accept standard TTL logic levels and drive inductive loads such as DC and stepping motors [9]. Two enable inputs are provided to enable or disable the device independently of the input signals. L298 has 2 amperes per channel current capacity and it can support up to 45 volts for outputting. Moreover, L298 works well up to 16 volts without any heat sink. The Actuators (Motors and Wheels) There are many kinds of motors and wheels. Our choice depends on the robot function, power, speed, and precision. Actually, it is better to use gearbox motors instead of common DC motors because it has gears and an axle and its speed does not change towards the top of a hill or downhill. Motors are rated to operate at 1700 rpm at 7 volt nominal voltage. It is better to use wheels for line follower robots, instead of a tank system. We can use three wheels. Two of them are joined to the motors and installed at the rear of the robot and the other wheel is free and installed in front of the robot as a passive caster. To get better maneuver, robot uses two motors and two wheels on the rear and a free wheel on the front. The power supply is 7.6 V with a regulator. The designed robot has eight infrared sensors on the front bottom for detecting the line. Arm based microcontroller Stellaris and driver L298 were used to control direction and speed of motors. General view of the line follower robot that we built is shown in Fig. 1. The robot is controlled by the microcontroller. It performs the change in the motor direction by sending an appropriate signal to the driver IC according to the received signals from the sensors. Real Time Task Scheduling We built a light-weighted and high-speed robot because points are awarded based upon the distance covered and the speed of the overall robot. Therefore, we used two high speed motors and a highly sensitive signal conditioning circuit. The body weight and wheels radius have effects on the speed, too. The weight of the designed robot is around 300 gr. and it could be lighter. The photograph of the top and bottom views of the designed robot is shown in Fig. 1. The microcontroller sends instructions to the driver after processing the data received from sensors. The driver powers the motors according to the inputs. Actually the driver supplies positive voltage to one of the motor pins and negative voltage to the other. There are five states of movement: To move forward; both of the motors are turned on and rotate forward simultaneously. To move left; the right motor is turned on and the left motor is turned off. To move right; the left motor is turned on and the right motor is turned off. To move left fast; the right motor rotates forward and the left motor rotates backward. To move right fast; the left motor rotates forward and the right motor rotates backward. Most embedded system applications need to react to the inputs or environment changes in real time, which means that the accuracy of computations is as important as their timelines. Furthermore, digital control algorithms need a fixed sampling time interval for measuring inputs and delivering output commands. Therefore, the idea of applying interrupts for task scheduling is introduced in this work. IMAG0388 (a) IMAG0392 (b) Figure 1 Images show (a) top, (b) bottom views of the built line follower robot. The Quadratic Line-Detection Algorithm A better way of detecting the line position, compared to the other simple line-following robots, by using a quadratic interpolation technique is introduced. Eight reflective optical sensors were used, and the coordinate of the leftmost sensor was 0. To find out the correct position of the black line, we had to locate three consecutive sensors with higher output readings than the other five sensors as shown in Fig. 2. Assume that the coordinates of these 3 sensors are x1, x1+1, and x1+2, and the true shape of the sensor output values are in the range of [x1, x1+2] which can be approximated by a quadratic curve. One can then find the following relationships between the coordinates of the sensors and the output values: (1) (2) (3) The coordinate value, at which the output value of the quadratic curve is the maximum, is considered as the true position of the line. By using the basic calculus, one would know that the coordinate value is: (4) (5) (6) It is assumed that the coordinate for the center position of the line-following robot is 0. Therefore, the error e between the line position and the center position of the robot is e â‚ ¬Ã‚ ½Ã¢â€š ¬Ã‚  0â‚ ¬Ã‚ ­Ã¢â€š ¬Ã‚  x â‚ ¬Ã‚ ½Ã¢â€š ¬Ã‚  Ã¢â€š ¬Ã‚ ­x (7) Figure 2 The line detection algorithm via quadratic interpolation. PID Tracking Control Algorithm The popular proportional-integral-derivative (PID) controller was introduced in this project to make the robot follow the racing track. The error between the center of the sensors and the track to be followed was then processed by the PID controller to generate velocity commands for the right and left wheels. First, the controller calculates the current position and then calculates the error established on the current situation. It will then send commands the motors to give a rigid turn, if the error is extraordinary or a minor turn, if the error is small. Basically, the amount of the turn given will be proportional to the error. Of course this is a consequence of the proportional control. Even after this, if the error does not decline approximately to zero, the controller will then growth the degree of the turn further and further over time till the robot centers over the line. This is the result of the integral control. In the process of centering over the line, the robot may overshoot the target position and move to the other side of the line where the above process is followed again. Thus, the robot may keep oscillating about the line in order to center over the line. To reduce the oscillating effect over time, the derivative control is used. The proportional term is only a gain ampli fier, and the derivative term is applied in order to improve the response to disturbance, and also to compensate for phase lag at the controlled object. Pseudo Code for the PID Controller; Kp = 10 Ki = 1 Kd = 100 offset = 45 ! Initialize the variables Tp = 50 integral = 0 ! the place where integral value will be stored lastError = 0 ! place where last error value will be stored derivative = 0 ! place where derivative value will be stored Loop forever LightValue = read sensors ! read sensors. error = -x ! calculate the error using equation (7). integral = integral + error ! calculate the integral derivative = error lastError ! calculate the derivative Turn = Kp*error + Ki*integral + Kd*derivative powerA = Tp + Turn ! power level for motor A powerB = Tp Turn ! power level for motor B MOTOR A direction=forward power=PowerA MOTOR B direction=forward power=PowerB lastError = error ! save the current error end loop forever ! do it again. PID controller requires the Kp, Ki and Kd factors to be set to match wheeled line follower robots characteristics and these values depends on robot structures, actuators, sensors and other electronic components characteristics. There is no equation given in the literature to calculate Kp, Ki and Kd factors. It requires experimental trial and error technique until you get the favorite behavior. We defined these factors according to following guidelines; Start with low speed and setting values of Kp, Ki and Kd to 0. Then, try setting Kp to a value of 1 and observe the robot. The goal is to get the robot to follow the line even if it is extremely wobbly. If the robot overshoots and misses the line, decrease the value of Kp. If the robot cannot navigate a turn or seems listless, increment the Kp value with small steps. Once the mobile robot is able to follow the path, set Kd value to 1 and then try growing this value until you see less shake. Once the robot is fairly stable at following the line, assign a value of .5 to 1.0 to Ki. If the Ki value is extraordinary, the robot will shake left and right rapidly. If it is too low, you wont see any perceivable alteration. Since integral is increasing, the Ki value has a substantial impact. You may continue to retuning process with adjusting Ki by .01 increments. Once the mobile robot is tracking the line with reasonable accuracy, you can increase the speed and see if it is still able to track the line. Speed disturbs the PID controller and will require rearranging as the speed fluctuations. Results And Discusion A line following robot is programed with simple (on/off) control as a comparison purpose in evaluating the performance of the dynamic algorithm controlled robot. The results of the experiment are summarized in Table-1. From the data in the table, it can be observed that dynamic PID algorithm controlled robot has better performance in every criteria listed in the table compared to simple (on/off) control robot. The dynamic algorithm controlled robot has higher velocity, consumes less time to complete one whole circuit, tracks the line smoother and has lower tendency to astray from line compared to uncontrolled robot. Therefore this system can be used in training undergraduate students on dynamic PID algorithm control system, its application and implementation in the real world and the advantages that it offers. Fig. 3 shows the designed robot during race pits test. Figure 3 The designed robot on the race pits. Table 1- Experimental result for Line Following Robot. Criteria Dynamic PID algorithm Simple (on/off) Time to complete one whole circuit 47.6s 71.4s Line tracking Smooth Not so smooth Velocity 0.2m/s 0.14m/s Tendency to astray from line Low High Conclusion The designed wheeled line follower mobile robot has eight infrared sensors on the bottom for detecting the line. The controller board includes Stellaris LM3S811 micro-controller and the motor driver L298 which were used to control the direction and the speed of motors. The proposed dynamic PID algorithm derives the line follower locomotion by adequately combining the information from sensor module. Experimental results show that the proposed algorithm can successfully achieve target following in various scenarios, including straight line and circular motion, sharp-turn motion and S-shape line tracking. We are working currently to develop a more sophisticated algorithm which can perform faster line tracking with less energy consumption.

Assessment And Repair Of Fire Damaged Structures Engineering Essay

Assessment And Repair Of Fire Damaged Structures Engineering Essay This chapter explains how a structure is assisted and repaired after the aftermath of a fire. Often the initial response when looking over a fire-damaged structure is one of despair and horror at the extent of damage. This situation is shown by the amount of non-structural debris lying around together with the unpleasant smell of many combustion products. In most cases, the damage is not as severe as is at first thought, even though immediate decisions must be taken on the short-term safety of the structure and whether any temporary propping is necessary or, indeed, whether some demolition work is necessary. This judgment will often need to be taken very quickly after the fire and will generally be based on a visual survey and expert judgement. It should be pointed out that the assessment of fire damaged structures is very much a black art in that it relies heavily on experience.. 4.1 Visual Inspection The aim of the visual inspection is to determine: Structural stability of the structure and The extent and severity of the fire. 4.1.2 Structural Stability If possible, the original drawings for the structure should be consulted at this stage these allow assessment of how the structure transmits the applied loading and enables the principal load carrying members to be identified, as well as those providing structural stability. The inspection needs to check any excessive deformation, deflection or cracking in the main load-carrying members and integrity at the connections between the main members (1). It is vital to check for structural stability if excessive bowing of structural elements such as masonry cladding or internal compartment walls, which would be observed in the inspection stage of a structure. Anywhere the fire has only affected part of the structure, it is crucial that the inspection also extend to any part of the structure not damaged indirectly by the fire; it is possible that a significant redistribution of forces can occur into the unaffected part of the structure. For a example in the Broadgate fire scenario when the structure behaved during the fire in a totally different manner to the way it was designed, in that forces were redistributed away from the fire by columns acting in tension to transmit forces to the relatively cool upper stories of the structure(2). 4.1.3 Estimation of fire severity The first method of obtaining a rough estimate of the fire severity is by the use of the fire brigade records in terms of the number of vehicles called out, the length of time taken to fight the fire, the length of time between the fire being noted and the arrival of the brigade, the operation of any automatic fire detection or fire fighting equipment and the degree of effort required to fight the fire. The second method is to estimate the temperature reached in the fire by studying the debris caused by the fire and therefore it is essential that no debris is removed until such a study is carried out in order to maintain evidence. Provided the materials generating the debris can be identified, the knowledge may be used to give an indication of temperature reached, since most materials have known specific melting or softening temperatures. Table.1 gives typical melting temperatures of different materials that could be found in a fire according to the Building Research Establishment (BRE). material Behaviour Approximate temperature (ËÅ ¡C) Softening or collapse of polystyrene 120 Melting of polystyrene 250 Aluminium softens 400 Aluminium melts 650 Softening of glass 700-800 Melting point of brass 800-1000 Melting point of sliver 950 Melting point of copper 1100 Melting point of cast iron 1100-1200 Table.1: melting point data (Source: Parker and Nurse (1956) BRE) It is very important that care is taken in consideration when using data as the temperatures varies over the height of a fire compartment; therefore the original position of a particular artefact is important. This method of assessment only gives an Indication that particular temperatures were reached but not the duration of exposure to that temperature. The third method that is available to give an estimate in terms of either the standard furnace test duration or a known fire, is to measure the charring depth on any sizeable piece of timber known to have been exposed to the fire from the start of the fire. The charring depth can be related back to the standard furnace exposure since timber of known, or established, density can be assumed to char at a constant rate between 30 and 90 min standard exposure. The position of the timber specimen in the compartment should also be noted. A fourth method is to calculate the fire severity from estimates of the compartment size, the fire load density and the area of openings (ventilation factor). In practice, no one of the above methods is completely reliable and therefore a combination of methods must be used to give a reasonable answer. The visual inspection, once carried out, will have identified those areas which must be either immediately demolished (where the damage is beyond that capable of being repaired) or those areas which may be capable of being repaired if sufficient strength can be attained (1). The inspection will also identify where there is no, or only very apparent damage. If repair of a structure is considered feasible, then a much more detailed investigation is required to ascertain the extent and severity of any damage and the residual strength of the structure. To do this, it is first necessary to clear all debris from the structure and to clean as much smoke damage as possible to allow an unhindered examination of all surfaces. 4.2 Damage Assessment In order to carry out any assessment of damage on a steel structure a number of stages needs to be carried out. The first stage involves a complete fully detailed survey of the structure. The second stage ascertains the residual strength of both the individual members and of the complete structure. 4.2.1 Structural survey For all structures, the first stage is to carry out, where appropriate, a full line and level survey. This is required to assess the residual deformations and deflections in the structure. The measured deflections should be compared with those for which the structure was designed. Care should be taken to note the effect of any horizontal movements due to thermal actions during the fire. Such effects of horizontal movement are often apparent away from the seat of the fire (Malhotra, 1978; Beitel and Iwankiw, 2005). In steel structures, since most structural steels regain more strength on cooling, there will be a slight loss in strength. However, the resultant deformations are likely to indicate the state of the structure. In this case, it is important to assess the integrity of the connections; it is possible that bolts could have failed within the connection or could have become excessively deformed. Where the floors comprise of profile sheet steel decking and in situ concrete, examination should be made for any separation between the decking and the beams. This separation can still occur even if thorough deck stud welding was used. Another potential point of failure is the shear bond between the decking and the in situ concrete. Fig 4.1 shows concrete separated away from the metal deck floor. Even with substantial damage of the types mentioned above, the structure may still be intact as demonstrated after the fire tests on the steel frame structures at Cardington (Bailey, 2004a)(6). Fig 4.1 Measurement of the gap of concrete gap after the fire (http://www.google.ie/images) Whilst carrying out the visual survey, attention should be given to the need for carrying tests on the structural materials to ascertain their residual strengths. The testing methods used may either be non-destructive or involve the taking of samples from damaged portions on the structure, together with control specimens from undamaged areas. 4.3 Testing There are two approaches that may be used to assess residual steel strengths for steel. The first is to remove test coupons or samples and subject those specimens to a standard tensile test.Fig.4.1 shows test results for a piece of S350GD+Z structural steel. Great Care should taken in removing test specimens in that the damaged structure is not further weakened, and that again any necessary propping should be used. Fig 4.2 Tensile test results for structural steel S350GD+Z, the test pieces taken before and after high temperature compression tests, where the material reached temperatures up to 950 °C, (Y. C. Wang P6) The second is to use non-destructive tests of which the most suitable is a hardness indentation test usually measuring the Brinell hardness. There is a direct, sensibly linear, relationship between the Brinell hardness number (BHN) and tensile strength as shown in fig.4.2. It is important that care is taken in using this test since a number of results are needed before the strength estimates are statistically reliable. Fig4.2: Relationship between steel strengths and Brinell hardness number (BHN) (Kirby, Lapwood and Thompson, 1986, p 370). 4.3.1 Residual strength For Grade 43A (S275) steel there is no residual strength loss based on the 0,2% proof s0 tress when the steel is heated to temperatures up to 600à ¢- ¦C but a 30% reduction at a temperature of 1000à ¢- ¦C(5). The variation in residual strength between these temperatures is sensibly linear. The pattern for Grade 50D (S355 J2) steel is similar except that the strength loss at 1000à ¢- ¦C is only about 15%. It should be noted that in all the tests, except for the American steel at 800à ¢- ¦C, the measured tensile strengths exceeded the minimum guaranteed yield strength. Data on such steels are presented in Fig. 4.4 (Holmes et al., 1982), where it is seen that the yield strength for reinforcing steel shows an increase above ambient strength at temperatures below about 550à ¢- ¦C, but a decrease at temperatures above 550à ¢- ¦C. Pre-stressing steels show no change in strength below 300à ¢- ¦C, but a substantial drop after this point such that at 800à ¢- ¦C only around 50% of strength remains Wrought iron appears to show a marginal strength increase at temperatures up to 900à ¢- ¦C and thus appears able to perform well in a fire provided however, that excessive deformations do not occur. Cast iron will also perform reasonably well unless undue large bending moments are applied to the member during the fire. The good fire performance in real structures is in part due to the very low stresses to which cast iron members were subjected in design. One problem that can occur is that brittle failure is possible if cast iron is quenched by cold water from firemens hoses whilst still red-hot, or if additional loads are induced during the fire (7). Fig.4.4: Variation of residual strengths of reinforcing and pre-stressing steels with temperature (Holmes et al., 1982). 4.4 Methods of repair As far as steelwork is concerned, any repair will be in the form of partial replacement where the original structure has deformed beyond the point at which it can be reused. Where the steelwork is still intact, it is almost certain that the fire protection system used will need partial or total replacement. Any intumescent paint systems will certainly need renewing. 4.5 Demolition of fire damaged structures Clearly, the same safety hazards that exist for structures being demolished for reasons other than fire damage exist for those so damaged; except that problems of stability are exacerbated for fire-damaged structures as the structure itself is naturally weaker, often to such an extent that little physical effort may be needed for demolition. 4.6 Re-use of steel after a fire An often quoted general rule for fire affected hot rolled structural steels is that if the steel is straight and there are no obvious distortions then the steel is probably still fit for use. At 600 °C the yield strength of steel is equal to about 40% of its room temperature value; it follows therefore that any steel still remaining straight after the fire and which had been carrying an appreciable load was probably not heated beyond 600 °C, will not have undergone any metallurgical changes and will probably be fit for re-use. However, where the load in the fire was less than the full design load, and also with high strength steels, this cannot always be held to be true. In such cases it is recommended that hardness tests are carried out on the affected steel. In practice it is recommended that, in all instances, some hardness tests should be carried out. For grade S275 steel, if the ultimate tensile strength resulting from the tests are within the range specified in  the table 2 below, then the steel is reusable. Table.2Ultimatetensilestrengths (source:http://www.corusconstruction.com/en/design_guidance/structural_design) For grade S355 steel additional tensile test coupons should be taken from fire affected high strength steel members when hardness tests show that: There is more than 10% difference in hardness compared to non-fire affected steelwork, or Hardness test results indicate that the strength is within 10% of the specified minimum. Where deflections are visible, general guidelines on the maximum permissible levels of deflection to ensure satisfactory performance are difficult to specify. The amount of deflection or distortion must be checked so that its effect under load can be calculated to ensure that permissible stresses are not exceeded and the functioning of the building is not impaired. Therefore every building should be considered as a separate case and the structural engineer involved in the reinstatement exercise must decide what level is acceptable to satisfy the relevant Codes. 4.7 Conclusion It can be concluded that the assessment of steel structures after a fire is crucial in order to judge the structural stability of the structure and seen can the building can be reused after the fire. Steel structure can behave different that they have been designed for and this can have a effect on the structural stability of the building, for example the broadgate fire behaved in a different manner than it designed for. It is essential that testing of steel is carried out after the fire in order to see if the steel is capable of been reused.It can be conclude that for Grade 43A steel there is no residual strength loss based on the 0,2% proof stress when the steel is heated to temperatures up to 600à ¢- ¦C but a 30% reduction at a temperature of 1000à ¢- ¦C. The variation in residual strength and temperatures has a linear relationship as they are directly proportional to each other. [1] Steel Construction Industry Forum (SCIF), 1991. Structural Fire Engineering: Investigation of Broadgate Phase 8 Fire, Steel Construction Institute, UK. [2] Fire Safety Engineering Design of Structures Second Edition John A. Purkiss BSc(Eng), PhD [3] Outinen,J.Mà ¤kelà ¤inen,P.,2004.Mechanical properties of structural steel at elevated temperatures and after cooling Fire and Materials, 28 (2-4), pp. 237-251. [4] Kirby, B.R., Lapwood, D.G. Thomson, G., 1986. The Reinstatement of Fire Damaged Steel and Iron Framed Structures, British Steel Corporation (now Corus), London, p. 46 [5] Wang Y.C., Wald F., Tà ¶rà ¶k A., Hajpà ¡l M., 2008. Fire damaged structures, in Technical sheets Urban habitat constructions under catastrophic events, Print PraÃ…Â ¾skà ¡ technika, Czech Technical University in Prague. [6] Bailey, C.G. (2004b) Structural Fire Engineering Design: Materials Behaviour- Steel, Digest 487 Part 2, BRE. [7] Holmes, M., Anchor, R.D., Cooke, G.M.E., and Crook, R.N. (1982) The effects of elevated temperatures on the strength properties of reinforcing and prestressing steels. Structural Engineer, 60B, 7-13 [8] Barnfield,J.R. and Porter, A.M. (1984) Historic buildings and fire; fire performance of cast-iron structural elements. Structural Engineer, 62A, 373-80. 4.0 Assessment and repair of fire-damaged structures 4.1 Visual Inspection 4.1.2 Structural Stability 4.1.3 Estimation of fire severity 4.2 Damage Assessment 4.2.1 Structural survey 4.3 Testing 4.3.1 Residual strength 4.4 Methods of repair 4.5 Demolition of Fire-Damaged Structures

Roman Religions :: essays research papers

The ancient Romand worshiped many gods, godesses and spirits, each of whom was responsible for a different part of life. Juno was the goddess of woman; Jupiter, the king of the gods was also the god of the sky; Mercury was the god of merchants; Wulcan the god of fire; Mars the god of war; Minerva the goddess of wisdom; Venus the goddess of fertility and love. The ancient Romans adopted gods and goddesses from other cultures as well. Bacchusor or Dionysus, the Greek god of wine; Cybelle, the Turkish goddess of motherhood; and Isis from the Egyptian pantheon who was concerned with reincarnation. Emperors and empresses were sometimes worshiped after their deaths.   Ã‚  Ã‚  Ã‚  Ã‚  Emperors showed their devotion to their favored deities by building temples to them. Roman citizens left offerings such as food, milk, wine, money, jewels or statues at temple alters and engaged in ceremonies and animal sacrifices to win the gods approval.   Ã‚  Ã‚  Ã‚  Ã‚  The Romans were generally accepting of other people’s religions but persecuted the Christians because, among other things, they displeased the gods by refusing to patricipate in such animal sacrifices and unjust ceremonies. Christianity finally because the official religion during the 4th century in Rome.   Ã‚  Ã‚  Ã‚  Ã‚  The Romans built large temples for these many gods. They were often built in places that people believed were special to their gods. The Acropolis, in Greece is one of these places.   Ã‚  Ã‚  Ã‚  Ã‚  In ancient Greece, the Greeksk alson believed in many gods and goddesses. The gods behaved much like ordinary people, but they had great wisdon. They were wiser, more cunning, and more powerful. The gods not only controlled nature, but they also controlled people’s fate. There were 12 main gods of the Greek belief, known as the Olympians. Some of the most famous included Zeus, Athena, Poseidon, and Apollo.   Ã‚  Ã‚  Ã‚  Ã‚  When you walked into a Greek or Roman temple, you would find a statue of a god or goddess at the end of a long, dark room. A row of columns ran down the center of the room along both sides. A worshiper of the time might have visited the temple to thank the god for a favor and leave them a gift.   Ã‚  Ã‚  Ã‚  Ã‚  The inside of the temple wasn’t a gathering place for worship like churches and sacred buildings of today. Worship services were held outside on an alter. The temple protects the statur of the god from the weather and anyone who would come along and harm it.

Qualitative Research Critique Essay -- Advanced Nursing Research

Article Citation Gilmartin, J. (2003). Day surgery: Patients’ perceptions of a nurse-led preadmission clinic. Journal of Clinical Nursing 13, 243-250. Initial Reaction This research article is from the UK and the writer questions if the findings from this study will have heuristic relevance and applicability to nursing and healthcare in the United States (U.S.). Primary healthcare in the UK is provided through the National Health Service (NHS); this writer has little knowledge as to how it works and its impact on patient care and nursing. This limited knowledge may introduce bias in this critique. Descriptive Vividness The significance of this study is to determine if a preadmission clinic process can be developed and implemented to positively impact the physical, psychological, and social healthcare needs of patients undergoing day surgery. The purpose of this study is â€Å"to elucidate patients’ perceptions of the preassessment preparation prior to day surgery† (Gilmartin, 2003, p. 244). This researcher identifies four themes related to patients’ perceptions of the preassessment preparation prior to day surgery; efficient functioning, assessment of patient suitability, the experience of information giving, and the problem of cancellation. Minimal excerpts are provided for three of the four themes; the fourth theme, the problem of cancellation is completely in narrative format. Although the emphasis of the findings was on the majority of excerpts, this researcher included negative case studies under two themes; efficient functioning and the experience of information giving. Efficient functioning was described by the majority of participants as being provided to in a timely manner, in contrast some (numbers not men... .... This study could have been improved by expanding the sample group from various preassessment clinics and to include diverse ethnicities and representation across various surgical specialties. In addition, another credible author would have increased trustworthiness of the entire study. This writer suggests the study be replicated in the U.S., with the suggested enhancements, for application in the U.S. healthcare system. Works Cited Burns, N., & Grove, S.K. (2009). The practice of nursing research: Appraisal, synthesis, and generation of evidence (6th ed.). St. Louis, MO: Saunders Elsevier. Gilmartin, J. (2003). Day surgery: Patients’ perceptions of a nurse-led preadmission clinic. Journal of Clinical Nursing 13, 243-250. Tappen, R.M. (2011). Advanced nursing research: From theory to practice. Sudbury, MA: Jones & Bartlett Learning.

History of Table Tennis Essay

The sport got its start in England towards the end of the 19th century when, after dinner, some upper-middle class Victorians decided to turn their dining room tables into miniature versions of the traditional lawn tennis playing field. Several different every-day objects were employed in constructing the sport. They used a line of books as the net. Rackets were lids from empty cigar boxes, and a little later, parchment paper stretched around a frame. The ball would be either a ball of string, or perhaps more commonly, a champagne cork or rubber ball. Before â€Å"Table Tennis.† When the game first started it was called by a number of different names. â€Å"Whif whaf,† â€Å"gossamer,† and â€Å"flim flam† were commonly used to describe it. The words, as can be assumed, were derived from the sound that the ball made when hit back and forth on the table. In 1901 though, English manufacturer J. Jaques & Son Ltd registered one of the more popular names, Ping-Pong, as a copyright. He later sold the trademark to the Parker Brothers in the United States. Then in the 1920’s the name and the sport were revived in Europe as table tennis. Evolution The turn of the century brought many other refinements to the sport. Players started using celluloid balls after the English man James Gibb discovered them during a trip to the United States in 1901 and proved them to be perfect for Ping-Pong. In 1903, E.C Goode replaced parchment paper and cigar box lids with pimpled rubber on light wooden â€Å"blades† as rackets. And after the world championships in Prague in 1936, where two defensive players took over an hour to contest one point, the net was lowered to make the pace of the game-play faster. (In another effort to make the game more fast paced and entertaining, rules were again changed in 2001- see Rules). It Spreads Also around this time, the sport spread to other European countries and to the United States. Asian countries like China, Korea and Japan are understood to have learnt about it from British Army officers who held posts in those places. There was an unofficial world championship held in 1901, but the first official world championship was held in London in 1927 by the International Table Tennis Federation. The ITTF was founded in Berlin in 1926 by England, Sweden, Hungary, India, Denmark, Germany, Czechoslovakia, Austria, and Wales. Asian Factor Although it may seem today that the sport, in the professional realm, is dominated by Asian countries like China and Korea, it wasn’t always that way. Before the late 1950’s and early 60’s, European players from Hungary especially, but also from France and Sweden seemed without competition. But in 1952, Japanese player Horoi Satoh introduced the foam rubber paddle. The paddle made the game faster and spinning the ball became an even greater factor. Japan became the main winner in the world competitions in 1960, and by the mid 1960’s China took over the reigns through to the early 1980’s. Their absolute domination of the sport was finally subdued with the entering of table tennis into the Olympic Games in 1988 and the participation of players from Korea and Sweden. Table Tennis and the Cold War On April 6th, 1971, the US table tennis team was invited on an all-expenses-paid trip to play in China. Four days later, nine players, four officials and two spouses crossed the bridge from Hong Kong to the Chinese mainland. They were the first group of Americans to be allowed into the country since the communist take-over in 1949. One of the first signs during the Cold war of improved relations between the United States and China, Time magazine called it â€Å"the pong heard throughout the world.† It was shortly followed with a visit to China by President Nixon. Facilities and Equipment The Table The playing surface, should be rectangular, 2.74m long and 1.525m wide, and shall lie in a horizontal plane 76cm above the floor .The playing surface should not include the vertical sides of the tabletop. The playing surface should yield a uniform bounce of about 23cm when a standard ball is dropped on to it from a height of 30cm. The playing surface shall be uniformly dark colored and matt, but with a white side line, 2cm wide, along each 2.74m edge and a white end line, 2cm wide, along each 1.525m edge. The playing surface shall be divided into 2 equal courts by a vertical net running parallel with the end lines, and shall be continuous over the whole area of each court. For doubles, each court shall be divided into 2 equal half-courts by a white center line, 3mm wide, running parallel with the side lines; the center line shall be regarded as part of each right half-court. The Net Assembly The net shall be suspended by a cord attached at each end to an upright post 15.25cm high, the outside limits of the post being 15.25cm outside the side line. The top of the net, along its whole length, shall be 15.25cm above the playing surface. The Ball The ball shall be spherical, with a diameter of 40mm.and weigh 2.7g. The ball shall be made of celluloid or similar plastics material and shall be white or orange, and matt. The Racket The racket may be of any size, shape or weight but the blade (wooden face) shall be flat and rigid. The covering material (rubber sheets) shall extend up to but not beyond the limits of the blade, except that the part nearest the handle and gripped by the fingers may be left uncovered or covered with any material. The surface of the covering material on a side of the blade, or of a side of the blade if it is left uncovered, shall be matt, bright red on one side and black on the other. Slight deviations from continuity of surface or uniformity of color due to accidental damage or wear may be allowed provided that they do not significantly change the characteristics of the surface. Rules of the game Serving The server shall project the ball near vertically upwards, without imparting spin, so that it rises at least 16cm and then falls without touching anything before being struck. The ball shall not be hidden from the receiver by any part of the body or clothing of the server or his doubles partner and as soon as the ball has been projected, the server’s free arm shall be removed from the space between the server’s body and the net. If the umpire is doubtful of the legality of a service he may, on the first occasion in a match, declare a let (see below) and warn the server. Any subsequent service of doubtful legality of that player or his doubles partner will result in a point to the receiver. Whenever there is a clear failure to comply with the requirements for a good service, no warning shall be given and the receiver shall score a point.

Hydrostatic Lab Report

ABSTRACT On the past two weeks, I have done an experiment on hydrostatics, or is also known as fluid statics (fluid at rest) within the fluid mechanics field of study. This condition explains that in a stable condition, the fluid is at rest. The use of fluid in doing work is known as hydraulics, and the science of fluid in motion is known as fluid dynamics. INTRODUCTION The natural nature of fluids are they cannot remain stationary under the application of shear stress. However, fluid can apply force normal to any surface contacting it.If the fluid is considered as a solid object such as a cylinder, the pressure acting on a surface is the same as the pressure on the opposite side of the object, but in a different direction. This condition can be applied to any surface on the imaginary fluid shape. This thus defines that the pressure on a fluid is isotropic, meaning that the force/pressure in any direction applied on the liquid is the same in all directions. Hydrostatic Pressure Hydro static pressure is the pressure exerted by a fluid at equilibrium due to the gravitational pull. The fluid is known as hydrostatic fluid.The pressure can be calculated from the control volume analysis of a small cube of fluid. It is known that pressure is force applied per unit area P = F/A, and the onlyforce acting on any such small cube of fluid is the weight of column above it, we can calculate the hydrostatic pressure by: The sumary of the theory is the force on any flat surface is the average pressure acting on the submerged surface multiplied by the area of the submerged surface. F = ? gXA Where: ? = water density g = acceleration due to gravity X = vertical distance from free surface to centroid of AWe know that the magnitude of the distributes force F, which may be considered as a small series of small forces spread over the submerged surface. The sum of the moments of all these small forces about any point must be equivalent to the moment about the same point of the resulta nt force Fr acting through the point of application, also known as the center of pressure. Taking the moments about O : Force on strip ? F=x? g ? A Moment of force an strip ? M=x2? g ? A But we know that : Sum of [x2 ? A] = 2nd moment of area (I? ) Therefore total moment = ? gI?Therefore Frz = ? gI? and since Fr = F = ? g A X z= ? gI gAX= I? AX= 2nd moment of area about ‘oo'1st moment of area about ‘oo' z= I? AX from parallel axis theorem I? =Igg+ AX2 Therefore, substituting z= Igg+ AX2AX z= IggAX+ X Xc=z+q For a partially submerged plate, the same equations apply except that the area of the plate varies. (A = br) Since Igg = br312 And substituting A = br and X = r2 in the equation for z: z= 23r It can be clearly seen that the centre of pressure is always two-third down the section of the submerged part of the plate. Xc= 23r+q Procedure: – The quadrant is placed on the two dowel pins and the clamping screw is fastened to the balance arm using the clamping screw. L , a, depth d, and width b, of the quadrant end face are measured. 2- With the Perspex tank on the bench, the balance arm is balanced on the knife edges (pivot). The balance pan is hung from the end of the balance arm. 3- A length of hose is connected from the drain cock to the sump and a length from the bench feed to the triangular aperture on the top of Perspex tank 4- The tank is then levelled using the adjustable feet and spirit level.The counter balance weight is moved until the balance arm is horizontal. 5- The drain cock is closed and water is admitted until the level reaches the bottom edge of the quadrant. A weight is placed on the balance pan, and water is slowly added into the tank until the balance arm is horizontal. The water level on the quadrant and the weight on the balance pan is recorded. 6- Fine adjustment of the water level can be achieved by overfilling and then slowly draining using the stop cock. 7- The above are repeated for each increment of weight until the water level reached the top of the quadrant end face.Then each increment of weight is removed, noting the weights and water levels until the weights have been removed. RESULTS AND DISCUSSION a= 0. 099m b= 0. 075 m d= 0. 100m l= 0. 274 m ?= 1000 kg/m Weight of load, m(kg ms-2)| Filling tank height of water(m)| Draining tank height of water (m)| Average height of water,y (m)| Wetted surface area, yb (m )| Hydrostatic pressure, m/yb (Pa)| 0. 3924| 0. 040| 0. 041| 0. 041| 0. 003075| 127. 6098| 0. 5886| 0. 050| 0. 050| 0. 050| 0. 003750| 156. 9600| 0. 7848| 0. 058| 0. 058| 0. 058| 0. 004350| 180. 4138| 0. 9810| 0. 065| 0. 065| 0. 065| 0. 004875| 201. 308| 1. 1772| 0. 072| 0. 073| 0. 073| 0. 005475| 215. 0137| 1. 3734| 0. 078| 0. 077| 0. 078| 0. 005850| 234. 7692| 1. 5696| 0. 084| 0. 083| 0. 084| 0. 006300| 249. 1429| 1. 7658| 0. 089| 0. 088| 0. 088| 0. 006600| 267. 5455| 1. 9620| 0. 094| 0. 094| 0. 094| 0. 007050| 278. 2979| Graph of my2 against y Where the slope is -? b2L and the interc ept should be ? b2L(a+d) Therefore ?b2L = -93. 9097 ?b2L(a+d) = 101. 7810 CONCLUSION REFERENCE 1- www. wikipedia. org on hydrostatic pressure 2- www. scribd. com on hydrostatic pressure lab report 3- Experiment manual 4- Lab demonstrator’s explanation